Possible issue.

[ChickenCanoe]

It's sad you lost your amazing cat. I can imagine.

 

[Ridgerunner]

I have an irrigation ditch that runs through my property. I plan to, eventually, free range during the day. I will keep them corralled until they are older then slowly introduce them to the area. Question: should I be concerned with them drowning themselves in the ditch?

I would not be concerned. With living animals anything is possible but for thousands of years people have raised chickens around ponds, creeks, rivers, lakes, and other bodies of water. Whether feral or raised on these farms these bodies of water are generally where they drink their water. Chickens are not extinct yet. I'd worry about predators a whole lot more than of them drowning.

Chickens cannot launch themselves into flight from a body of water, not like ducks or other waterfowl whose feathers remain dry. But they will float, even if their feathers get wet. And while floating they can sort of swim/dog paddle to move around. The danger would not be from them drowning but from hypothermia. Ad while they might wade in water to cool off in hot weather they are not likely to fall in.

So, yes, in my opinion you are worrying about something you really do not need to worry about.